Unitized pump system

ABSTRACT

A unitized pump system including a drive means for driving a common low-speed booster stage that receives all inlet fluid for the pump system, a low-flow centrifugal stage that supplies the low-pressure and flow requirements of the system, a high-flow centrifugal stage that furnishes the high-pressure and flow requirements of the system and a cranking stage comprising a high-speed gear pump driven by a hydraulic coupling of the drive means which coupling is drained when the low-flow stage is operating with a sufficient discharge pressure and which coupling is filled when the low-flow centrifugal stage becomes disabled to drive the cranking stage as an emergency backup stage. The discharge line of the cranking stage includes a pressure regulated system for emergency pressure control of the cranking stage discharge during emergency operation which pressure regulating system includes a temperature override mechanism to prevent overheating of the fluid being recirculated to the booster stage.

United States Patent [72] Inventors Otto J. Danker;

Paul Cooper, both of Cleveland Heights, Ohio [211 App]. No. 772,928 [22] Filed Nov. 4, 1968 [45] Patented June 29, 1971 (73] Assignee TRW Inc.

Cleveland, Ohio [54] UNITIZED PUMP SYSTEM 14 Claims, 8 Drawing Figs.

[52] US. Cl r. 417/47, 417/203, 4l7/205,4l7/2l6,4l7/248, 417/253, 417/292 [51 1 Int. Cl ..F04b 49/00, F04b 23/14, F04b 41/06 [50] Field of Search 60/3928; 103/11, 126, 23; 417/3, 4, 47, 203, 205, 216, 248, 253, 292, 308

[5 6] References Cited UNITED STATES PATENTS 1,884,739 10/1932 Kinsella 103/11 2,740,469 4/1956 C0lestock.. 60/3928 2,781,727 2/1957 Marshall (SO/39.28 2,916,875 12/1959 Morley et a1 60/3928 y "-w 8,9 \,7 I. g l k I I1. I

2,946,190 7/1960 Corbett 103/1 1 3,011,308 12/1961 Wotring 103/11 3,068,795 12/1962 Lauck 103/1 1 3,433,016 3/1969 Borel 103/11 2,767,658 10/1956 Murray 103/126 Primary ExaminerWilliam L. Freeh Auorney-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: A unitized pump system including a drive means for driving a common low-speed booster stage that receives all inlet fluid for the pump system, a low-flow centrifugal stage that supplies the low-pressure and flow requirements of the system, a high-flow centrifugal stage that furnishes the highpressure and flow requirements of the system and a cranking stage comprising a high-speed gear pump driven by a hydraulic coupling of the drive means which coupling is drained when the low-flow stage is operating with a suff cient discharge pressure and which coupling is filled when the lowflow centrifugal stage becomes disabled to drive the cranking stage as an emergency backup stage. The discharge line of the cranking stage includes a pressure regulated system for emergency pressure control of the cranking stage discharge during emergency operation which pressure regulating system includes a temperature override mechanism to prevent overheating of the fluid being recirculated to the booster stage.

I a ,IIIIIIIIIII/l, V 4/ II M i llllll 7 -!J I IIIIII UNITIZED PUMP SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a fluid pump system having pumping stages of different capacities which are utilized to respond to the output demands placed on the system.

2. Description of the Prior Art An aircraft jet engine during a normal flight operation experiences a large variation in fuel requirements or demands. One solution for meeting the variations in fuel requirements of the jet engine is the provision of the single high-capacity pump with a flow bypass for returning the excess discharge of the pump back to the pump inlet or the fuel supply or tank. The bypassing of a pumps discharge has the disadvantage of causing the pump to be inefficient while the jet engine is in a cruising condition, and the pumps inefficiency creates an undesirable rise in the temperature of the fuel being recirculated to the pump inlet or the fuel supply or tank.

Another solution for supplying the fuel demands of a jet engine has been the provision of separate pumps with separate discharge lines to the engine, each of the pumps is designed to provide the necessary fuel requirements for a particular operating condition of the jet engine. Each of the pumps has control means to valve the pump in and out of operation depending upon the particular requirements of the engine. Since such system necessitates separate drive means and control systems for each of the pumps, the combined weight of the separate pumps for a jet engine is increased over that of a single pump system, and, therefore, the separate pumps are undesirable.

SUMMARY OF THE INVENTION The present invention is directed to a unitized fuel-pumping system, the various pumping elements are combined in a lowweight package that furnishes all the fuel requirements for a jet engine from a single discharge port. The unitized fuel pumping system includes a low-flow centrifugal stage which supplies the lower flow and pressure fuel requirements such as experienced at idle and cruise speeds of the jet engine, a highflow centrifugal stage that furnishes the high flow and pressure fuel requirements for high-power engine operation such as experienced at takeoff, and a cranking stage driven by a hydraulic coupling which is drained when the low-flow stage is operating at sufficient pressure. Each of the stages are contained within a single housing which has a fuel supply inlet means to supply the inlets of each of the stages and a common outlet port to receive the discharge of each of the stages.

Accordingly, it is an object of the present invention to provide a unitized pump system in which all flow modulation is accomplished by simple throttling which does not require the bypassing of the output of the pump systems.

Another object of the present invention is the provision of a unitized fuel pump system for furnishing the demands of the engine, in which each of the stages are operating at maximum efficiency and have a minimum rise in fuel temperature due to the pumping inefficiencies.

Yet another object of the present invention is a unitized pump system having a combined low weight and furnishing all the flow requirements of an engine from a single discharge port.

Yet another object of the present invention is the provision of a unitized pump system having an oil-lubricating section which contains the drive means, and which is sealed from the pump stages to prevent the liquid being pumped from contamination by the lubricating oil.

A still further object of the present invention is the provision of a unitized pump system utilizing centrifugal stages to minimize damage by contamination in the liquid being pumped.

A still further object of the present invention is the provision of a pumping system having a cranking stage driven the stages fails to function properly.

Yet another object of the present invention is the provision of a pump system having a temperature override mechanism in a fluid bypass device for the pump output to limit the temperature increase in the bypassed fluid.

These and other objects, features and advantages of the present invention will be understood in greater detail from the following description and associated drawings wherein reference numerals are utilized in describing an illustrative embodiment.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of the various pumping stages of the present invention showing their interrelationship and coaction; I

FIG. 2 is a cross section of the unitized fluid-pumping system with portions shown in elevation for purposes of illustration and with the control means for the coupling broken away and shown in an enlarged cross section;

FIG. 3 is an end view with portions broken away for purposes of illustration of the unitized fluid-pumping system;

FIG. 4 is a partial erid view with a different portion broken away at the outlet port of the pumping system;

FIG. 5 is an end view of the outlet port taken from line V-V of FIG. 3; I

FIG. 6 is a partial cross section of a volute drain valve for the main volute of the highflow stage of the unitized pumping system;

FIG. 7 is a partial cross section of a volute bleed valve for the volute of the high-flow stage; and

FIG. 8 is a cross section with parts in elevation of a pressure regulator valve of the cranking stage of the pumping system.

DESCRIPTION OF THE PREFERRED EMBODIMENT A unitized fuel pump system generally indicated at 10 in FIG. 2 comprises a housing generally indicated at 11 which is made up of three pieces joined together by fastening means such as bolts 12.'The housing 11 has a pumping section and an oil-lubricating section. The pumping section includes an inlet supply means 13, which includes a booster stage or pump means 14, a cranking stage or gear pump means 15, a low-flow stage or pump means 16, and a high-flow or high-capacity stage or pump means 17, and an outlet port 18.

Disposed in the lubricating section of the housing 11 is a drive means generally indicated at 19 which includes a main drive shaft 20 having a gear 21 adapted to be engaged by a power source for the drive mans 19. The drive shaft 20 is journaled in the housing 11 by bearings such as 22 and 23and is connected to an impeller 24 of the high-flow pump means 17. To isolate the pump means 17 and to prevent the lubricating oil of the lubricating section from contaminating the output of the pump means 17, seals 25 are provided between the pump means 17 and the bearing 22. The main drive shaft 20 includes a drive gear 26 which drives gears 27 and 28 with gear 27 being mounted on a drive shaft 29 and a gear 28 being mounted on a drive shaft 30. The shaft 29 is journaled in the housing 11 by hearing means 31, 31 and is connected to an impeller 33 of the low-flow pump means 16. To prevent lubricating oil in the lubricating section of the housing from coming in contact with the impeller 33, seal means 34 are provided on the shaft 29 adjacent the impeller 33 to isolate the pump means 16 from the bearing means 31 and the gear 27. The shaft 30 is journaled in the housing 11 by bearing means 35 and supports a gear 36 which is in meshing relationship with the gear 37 of a drive shaft 38. The shaft 30 terminates in a coupling means 39 which is preferably a fluid coupling that transfers the rotation of the shaft 30 to a shaft 41 which is journaled in the housing 11 by hearing means 42 and is connected to the cranking stage 15. To prevent oil from flowing into the cranking stage 15, seal means 43 are provided on the shaft 41. The shaft 38 is journaled in the housing 11 by bearing means 44 and is connected to an impeller 45 of the booster stage 14. To prevent the flow of oil from the lubricating section of the housing 11 into contact with the impeller 45, seal means 46 are provided on the shaft 38.

The gears 26, 27, 28, 36 and 37 of the drive means 19 are selected so that each of the shafts 20, 29, 30 and 38 rotate at a different speed. For example, when the main shaft 20 is rotating at 24,000 r.p.m. the shaft 29 is rotating at 40,000 r.p.m. while the shaft 38 is rotating at 6,500 r.p.m.

H6. 1 best illustrates the connection and coaction between the various pumping stages of the pumping system 10. The output of the booster stage 14 which is a centrifugal-type pump is the volute 47 which is hereafter referred to as the interstage. The cranking stage 15 includes an inlet 48 for conducting fluid from the interstage 47 to the cranking stage and a discharge line 49 including a check valve 50 which discharges the output of the cranking stage to the common outlet port 18. A pressure control or pressure regulating valve 52 is connected to the discharge line 49 and the interstage 47 for limiting the maximum discharge pressure of the stage by returning a portion of the discharge of the cranking stage 15 back to the interstage 47.

The low-flow stage 16 includes an inlet 53 for conducting fluid from the interstage 47 to the pump means 16 and a discharge line 54 including a check and bleed valve 55 for conveying the discharge of the low-flow stage 16 to the common outlet port 18. The discharge line 54 also includes a pressure conduit 56 which is connected to a control means 57 which regulates the operation of the coupling means 39. The control means 57 includes a means responsive to the discharge pressure of the low-flow pump means or stage 16 and the control means switches the coupling means 39 from a condition connecting the cranking stage 15 to the drive means to a condition of disengaging the cranking stage from the drive means 19 to stop the operation of the cranking stage.

The high-flow pump means 17 has an inlet 59 including an inlet valve means 60 connected to the interstage 47 A discharge line 61 including a check valve 62 conveys the discharge of high-flow pump means 17 for discharge from the system through the common outlet port 18. The commonoutlet port 18 is connected to a gas generator and augmentation control device 63 for the jet engine, which device has a sensor which controls the operation of the inlet valve means 60 through a control circuit 64.

When starting the engine to which the pumping system is supplying fuel, the hydraulic coupling 39 is in the engaged position so that the shafts 30 and 41 are connected to drive the cranking stage 15 which is a high-speed gear pump. Even though the drive means 19 during starting of the engine is operating at about percent of its normal speed, the output of the high-speed gear pump is sufficient to supply the fuel requirements of the engine and continues to supply the fuel until the combined output of the booster stage 14 and the lowflow stage 16 reach the required pressure output to supply the engine requirements. When the confined output of the booster stage 14 and low-flow stage 16 reach a predetermined value, the control means 57 drains the fluid coupling 39 to disconnect the shafts 41 and 30. With the draining of fluid coupling 39, the cranking stage becomes inoperative, check valve 50 closes and the discharge of the low-flow stage 16 passing through the outlet port 18 supplies the needs of the device 63.

When the engine is required to operate at a high-power output, a sensor in device 63 sends a signal on the control line 64 to open the inlet valve 60 of the high-flow stage 17. The highflow stage 17 which was rotating in a valve-out condition will immediately begin pumping the fluid once the inlet valve means 60 is opened. The discharge of the high-flow pumping means 17 is sufficient to close the check valve 55. The check valve 55 of the discharge line 54 of the low-flow stage 16 when closed is provided with a bleed orifice to enable a small portion of the discharge of the high-flow pump means to bleed back through the low-flow pump means 16 to provide cooling thereof.

Since the low-flow pump means 16 is operating even while the discharge to the outlet port 18 is completely provided by the high-flow pump means 17, it is always in a standby condition ready to begin pumping at any time in which the flow demands or requirement of the device 63 are transmitted on the control circuit 64 to close the inlet valve means 60 of the inlet 59 of the high-flow pump means 17. Once the valve means 60 has been closed, the low-flow pump means 16 begins to supply the fluid requirements required by the jet engine.

By opening and closing the inlet valve means 60, the sensor of the control device 63 determines which of the pump means 16 or 17 will supply the fuel requirement of the jet engine. Preferably, a control margin is provided to prevent hunting in the control action of the device 63. Therefore, the inlet valve means is opened when a certain predetermined flow rate, such as 4,500 p.p.h., is required and the valve is closed when the required flow rate drops down to a lower preset flow rate such as 4,000 p.p.h. to provide a control margin of 500 p.p.h. on the control of the operation of the inlet valve means 60.

in an emergency situation such as a failure of the low-flow pump means 16 the output pressure in the line 56 to the control means 57 would drop and signal the control means which causes the hydraulic coupling 39 to be filled with fluid to connect the drive means 19 to the shaft 41 to start the rotation of the gear pump or cranking stage 15. Therefore, the control means 57 in conjunction with the hydraulic coupling 39 provides an emergency backup for the low-flow stage 16 by reactivating the gear pump 15. During its operation at higher speeds, the gear pump 15 may produce a-discharge flow rate having a pressure exceeding the demands of the control device 63 and this excess discharge pressure is relieved by passing through the pressure control or regulator 52 back to the interstage 47. As described hereinafter, the pressure control or pressure regulator means 52 includes a controlled bleed means to increase the operating pressure of pump means 15 during emergency operation and a temperature override or bypass to prevent overheating of the fluid which is recirculated.

In normal operation the cranking stage 15 is operated approximately 1 to 2 minutes during a flight operation of the engine. However, should either the low-flow or high-flow stage become inoperative, the cranking stage 15 will provide an emergency fuel supply for the engine. If a failure occurs only in the high-flow pump means 17, the low-flow pump means 16 can supply a quantity of fluid which, although insufficient for augmented operation of the airplane, such as takeoff or climbing, is still adequate for normal jet engine operations such as cruising.

The cranking stage 15, which is preferably a high-speed gear pump, has dry lift capabilities and can be used in making an air restart of the jet engine.

As best illustrated in FIGS. 2 and 3 the cranking stage 15 comprises a high-speed positive displacement gear pump having gears and 71 which are driven by the drive shaft 41 through a gear pump drive means 72.

The coupling 39 is disposed in a housing made of portions 73 and 74 of which 73 is integral with the housing 11. Fluid is introduced into the housing of the coupling means 39 through a hydraulic line 75 in the center of the shaft 30 which is also provided with a coupling air vent 76 for bleeding a small portion of the hydraulic fluid from the coupling for cooling purposes. The coupling means 39 is also provided with a drain orifree 77 which is connected to the control means 57 be a conduit 78, a portion of which is indicated for purposes of illustration as an arrowv line. The line 75 is connected to the control means 57 by a conduit 79 a portion of which is indicated by an arrow line.

The control means 57 for the coupling means 39 is illustrated in FIG. 2 as being broken away from the housing 11; however, it can be disposed on the housing or in a bore provided in the housing 11. The control means 57 has a cylindrical bore 80 which threadedly receives a' sleeve 81 provided with ports 82, 83, 84, 85 and 86. The port 82 is connected to the conduit 79, while the port 83 is connected to the conduit 78. The port 84 is connected to a conduit 87 which goes to a drain, while the port 85 is connected to a conduit 88 which is illustrated as being connected to the oil lubrication section of the housing 11 to receive the oil that is supplied to the coupling 39. The port 86 is connected to a conduit 89 which is connected to an overboard drain. The bore 80 is provided with an aperture 90 to which the conduit 56 leading from the discharge line 54 is connected, as shown by the line of arrows, and the bore is also provided with a series of sealing means such as the O-rings 91 to provide sealing between the axially spaced ports.

A spool valve member 92 having axially spaced port closing portions 93, 94 and 95 with a sealing means 96, such as an O- ring in a groove, between the portions 93 and 94 and a reduced diameter portion 97 between the portions 94 and 95, and the valve member 92 is slidably received in the sleeve 81. An adjustable spring means 98 biases the spool valve member 92 in one direction toward the illustrated or first position in which the portion 95 closes the ports 83, 84, the portion 93 closes the port 86 and the reduced diameter portion 97 enables flow between the ports 82, 85. Fluid pressure from the conduit 56 entering the aperture 90 and acting on an end surface 99 of the valve member 92 forces the valve member 92 axially against the spring means 98 to a second position in the sleeve 81 in which position the ports 82 and 85 are closed by the portion 94, the ports 83 and 84 are open for fluid passage therebetween and the port 86 is opened to receive fluid from the aperture 90. The spring 98 is adjusted by the means 100 so that a predetermined fluid pressure in the conduit 56 is required to shift the spool valve to the second position. The coupling 39 receives the oil or coupling fluid when the spool valve member 92 is in the first position and the coupling oil is drained from the coupling 39 when the valve member 92 is in the second position. As discussed above, the coupling is drained once the discharge pressure in conduit 56 of the lowflow stage 16 reaches a predetermined pressure; however, if a failure in the low-flow stage occurs, the spring 98 will shift the valve member to the first position to refill the coupling with fluid and thus reengage the cranking stage 15.

As discussed hereinbefore, the high-flowpump means 17 is provided with a valve means 60 in its inlet 59. As best illustrated in FIG. 2, the inlet 59 is provided with a valve seat 101 which cooperates with the valve member 102 whichis moved by an actuator 103 attached to the housing 11. Preferably the actuator 103 is a single acting hydraulic piston 104 which acts against a spring pressure supplied by a spring 105 to lift the valve member 102 from the valve seat 101 in the inlet 59. The control for the fluid acting on the single acting hydraulic piston 103 is provided by the sensor in the gas generator or augmentation control device 63. The sensor when sensing an increase in output flow requirement which indicates that the high-flow pump means is required, opens a valve of a pressurized fluid source to apply fluid pressure on the single acting piston 104. The pressurized fluid source can be either a separate pressurized control fluid or can be drawn from the discharge of one of the active pumps of the energized pumping system.

. When the flow demands of the jet engine drop, the sensor then operates a valve to drain the fluid pressure from the single acting piston 104 so that the spring pressure spring 105 forces the valve 102 into contact or 'seating engagement with the valve seat 101 to close the intake 59 of the high-flow compressor.

As described hereinabove, the output of the high-capacity or flow pump means 17 is directed through a discharge line 61 which is the volute of the pump means 17, to the outlet port 18. The volute 61 is provided with a volute drain valve 110 and a volute bleed valve 111 which are best illustrated in FIGS. 6 and 7 respectively. The purpose of the volute drain valve and volute bleed valve are to remove the fluid from the volute 61 when the valve means 60 has closed the inlet port 59.

The volute bleed valve 111 comprises a valve body 112 which is threaded into a threaded bore 113 which is in communication with the volute 61. The body 112 has an internal bore 114 in which a spring bias valve member 115 is disposed and acts against a seat 116 which has an aperture 117 in communication with the volute 61. Thebore 114 has an aperture 118 in communication with a bleed line 119 which extends from the bore 113 to the interstage 47. Fluid pressure in the volute 61 forces the .valve member 115 off the seat 116 and enables the fluid in the volute to bleed through the bleed valve 111 and the bleed line 119 back to the interstage portion 47 of the fluid supply means 13.

The volute drain valve 110 best illustrated in FIG. 6 is threaded into a bore 120 in communication with the volute 61 and comprises a threaded member 121 having internal threads 122 to receive a discharge line 123 (FIG. 3). The threaded member 121 supports a seat 124 upon which a valve member 125 acts. The valve member 125 is spring biased by a spring 126 and is held against the seat 124 by the fluid pressure in the volute 61. In operation, when valve means 60 is opened, valve 110 bleeds air from the volute 61 until the fluid pressure in the volute has reached a predetermined pressure at which the volute pressure closes the valve member 125 against the valve seat 124. Upon closing of valve means 60, the fluid pressure in volute 61 decays through the bleed valve 111 to a predetermined pressure at which time the valve member 125 is lifted off the valve seat 124 to dump the remaining fluid in the volute 61 through the drain line 123 to an overboard discharge.

As best illustrated in FIGS. 3 and 4, the check valve 50 for I the cranking stage 15 is a spring loaded valve member 130 which is lifted from its valve seat 131 by the pressure in the discharge line 49 and is closed by the loss of pressure in line 49 and/or by the higher pressure of the fluid in the cavity 132 of the outlet port 18 created by the discharge of either the lowflow or the high-flow pump means 16 and 17. The check valve means 62 comprising the spring-biased valve member 133 and valve seat 134 prevents the flow of the fluid from the cavity 132 into the discharge line 61. The check valve 55 for the lowflow discharge line 54 includes a valve seat 136 and a springbiased valve member 137 which has a bleed orifice 138 for allowing a small portion of the fluid in the cavity 132 to flow backwards through the low-flow stage 16 for cooling purposes while the high-flow stage 17 is in operation.

As best illustrated in FIG. 2, the impeller 24 and the impeller 33 of the stages 17 and 16 respectively are single shroud impellers which preferably are hydrodynamically balanced in the axial direction by provision of slots in the base plate of the impeller between the vanes (not shown).

As best illustrated in FIG. 8, the pressure control or pressure regulator valve 52 comprises a pressure regulator and relief valve means 140, a control bleed means 141 and a temperature override or bypass means 142 which are disposed in housing 144 which may be a portion of the housing 11 or a separate unit mounted thereon. In order to maintain a higher pressure rise from pump means 15 during emergency operation, under which conditions the bypass flow rate is greatly increased, control bleed means 141 is provided to restrict such bypass flow and increase the discharge pressure of pump means 15 to a predetermined pressure level. However, during reduced flow rates of emergency operation, the pressure rise of pump means 15 is considerably in excess of that required by device 63 and is accompanied by an excessive increase in fluid temperature. Therefore the temperature override means or mechanism 142 is provided in the pressure control or pressure regulating valve 52 to control the amount of temperature increase in the fluid being bypassed to the interstage 47 so that it does not exceed a permissible maximum temperature level. The housing 144 has a cavity 145 having a portion 146 which is in communication with the discharge line 49. Threadedly received in the portion 146 is a sleeve member 147 having internal threads, a valve seat 148 and ports 149. Slidably received in the sleeve 147 is a valve member 150 which is urged against the seat 148 by a spring 151 acting between the valve member 150 and a threaded adjustment member 152 which is threaded into the sleeve 147.

The cavity 145 of the pressure regulator valve means 52 has two outlets which is a passageway 154 in which the control bleed means 141 comprising a bleed orifice is disposed and a second passageway 155 which extends to a second valvereceiving bore 157 in the housing 144. The passageway 154 inserts an enlarged portion 158 of the bore 157. The bore 157 receives a sleeve 159 having a port 160 in communication with the passageway 155 and a second port 161 in communication with a third passageway 162 which is in communication with a discharge passageway 163 which extends from the portion 158 and is connected to the interstage portion 47 of the fluid supply means 13. A temperature responsive unit 165 which is part of the temperature override means 142 is mounted in the enlarged portion 158 and moves a valve member 166 in the sleeve 159 between a position closing the port 160 to a position opening the port 160. The temperature responsive unit 165 may be bellows or other unit which expands in response to the temperature of the fluid in the enlarged portion or counterbore 158.

in operation, a predetermined pressure in the discharge line 49 lifts the valve member 150 from the valve seat 148 enabling a portion of the fluid in the discharge line 49 to pass through the ports 149 into the chamber 146 and cavity 145. The fluid in the cavity 145 then passes through the control bleed means 141 into the passageway 154 through the counterbore 158 and the passageway 163 to be discharged into the interstage portion 147 of the fluid supply means 13. Under low-flow emergency operation, the increased bypass flow of pump means is increased in pressure by control bleed means 141 to a pressure in excess of that required by device 63. The increase in pressure results in an increase in temperature which causes the temperature responsive means 165 to move the valve member 166 to open the-port 160 for bypassing some of the fluid in the cavity 145 through the passageway 155 into the sleeve 158 from which the fluid flows either through the port 161 and the passageway 162 or through the counterbore 158 into the discharge passageway 163.

Although minor modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.

We claim as our invention:

1. A unitized pump system comprising a housing having a fluid supply means and an outlet port; a drive means disposed in said housing; a first, second and third pump means disposed in said housing, each of said pump means having a discharge means extending to said outlet port for conveying the output of each pump means thereto, each of said discharge means of said pump means including a check valve, each of said pump means having separate inlet means for receiving fluid from said supply means, the inlet means of said third pump means including a valve means for selectively opening and closing the inlet means of the third pump means to control the output therefrom, the second pump means includes means to feed a small amount of the output fluid from said outlet port to said second pump means so that said second pump means is prevented from overheating when the valve means of the inlet means of the third pump means is in an open position; said second and third pump means being connected to said drive means; and a coupling means including a control means for selectively interconnecting said first pump means to said drive means.

2. A unitized pump system according to claim 1, wherein said first pump means is a gear pump and said second and third pump means are centrifugal pumps.

3. A unitized pump system according to claim 1, wherein said fuei supply means includes a fourth pump means connected to said drive means.

4. A unitized pump system according to claim 1, wherein said drive means includes a drive shaft for each of said pump means, and gear means interconnecting each of said drive shafts so that each of said shafts and their respective pump means are driven by said drive means at a different speed.

5. A unitized pump system according to claim 1, wherein said third pump means is a high-capacity pump means, and wherein said valve means includes a valve seat formed in the inlet means of said third pump means, a valve member coactable with said valve seat and attached to an actuator means disposed in said housing said actuator being controlled by a sensor means responsive to flow demands of the fluid passing through said outlet port, so that when a high-capacity output is required from said system the actuator moves the valve member to an open. position enabling the high-capacity slide means to begin pumping.

6. A unitized pump system according to claim 1, wherein said means to feed of the second pump means is a small bleed orifice provided in the check valve of the discharge means for the second pump means.

7. A unitized pump system according to claim 1, wherein said control means of said coupling means is interconnected to the discharge means of the second pump means so that said control means is actuated by a preselected output pressure of said second pump means to disengage said coupling means.

8. A unitized pump system according to claim 7, wherein said coupling means is a fluid coupling having fluid input and discharge lines extending to a fluid pressure source, and said control means further includes a spool valve assembly disposed on said housing controlling flow in said input and discharge lines, the valve member of said spool valve assembly being moved to a position closing the inlet lines and opening the drain line by a preselected output pressure of said second pump means.

9. A unitized pump system according to claim 1, wherein the discharge means of the first pump means includes a pressure control means to divert a portion of the output flow of the first pump means to said fluid supply means.

'10. A unitized pump system according to claim 9, wherein said pressure control means includes a pressure regulator valve means being adjusted to maintain a predetermined discharge pressure of said first pump means, a control bleed means connected to the outlet of said regulator valve means for increasing the discharge pressure of said first pump means, and a bypass valve means connected between the outlet of the regulator valve and the outlet of the control bleed means to selectively bypass the control bleed means.

11. A unitized pump system according to claim 10, wherein said bypass means includes a temperature responsive unit disposed in the outlet of the control bleed means, said temperature responsive means being connected to a valve member of the bypass valve means so that said bypass valve member is moved to an open position when the temperature in the outlet of the control bleed means reaches a predetermined temperature to prevent overheating of the fluid passing through said outlet of said control bleed means.

12. A unitized pump system comprising a housing having a fluid inlet means and an outlet port; a booster pump disposed in the inlet means, said booster pump having a discharge passageway in said housing; a cranking stage disposed in said housing, said cranking stage having an inlet in communication with the discharge passageway of said booster pump and having a discharge line communicating with said outlet port; a low-flow stage disposed in said housing and having an inlet means in communication with the discharge passageway of said booster pump and a discharge line communicating with said outlet port; a high-capacity stage disposed in said housing having an inlet means in communication with the discharge passageway of said booster pump, said inlet means of said high-capacity stage including a valve means for selectively opening and closing said inlet means to control flow of fluid to said high-capacity stage, said high-capacity stage having a discharge line communicating with said outlet port, each of said discharge lines having a check valve, vent means between said outlet port and the discharge line of the low-flow stage to deliver fuel for cooling said low-flow stage when fuel is delivered by said high-capacity stage, a drive means disposed in the housing for driving each of said stages and the booster pump, said drive means including a coupling means for selectively interconnecting the drive means with said cranking stage, said coupling means including a control means for selectively engaging and disengaging said coupling so that said cranking stage is selectively driven by said drive means.

13. A unitized pump system according to claim 12, wherein said coupling means is a hydraulic coupling having a fluid supply port and a fluid drain port with the movement of fluid through said ports being controlled by said control means.

14. A fuel pump assembly for aircraft engines comprising a fuel supply pump, a high-speed positive displacement cranking stage pump receiving fuel from said supply pump, a highflow centrifugal pump also receiving fuel from said fuel supply pump, a low-flow centrifugal pump also receiving fuel from said fuel supply pump, said high-speed positive displacement cranking stage, low-flow centrifugal pump and high-flow cen tnfugal pump each having a separate discharge passage communicating'with a common outlet, 3 check valve between each separate discharge passage and said common outlet, a sensor controlling fuel flow to said high-flow centrifugal pump for controlling fuel discharge therefrom, vent means between said common outlet and the discharge passage of the low-flow centrifugal pump to deliver fuel for cooling said low-flow centrifugal pump when fuel is delivered by said high-flow centrifugal pump, means for driving said pumps, a disconnect coupling between said means for driving and said highspeed positive displacement pump, means controlled by pressure of fuel delivered from said low-flow centrifugal pump for disconnecting said coupling at a predetermined fuel pressure, whereby fuel from said fuel supply pump is pumped by said high speed positive displacement pump during engine cranking operations, is pumped by said high-flow centrifugal pump during high-powered engine operation and is pumped by said low-flow centrifugal pump during engine cruising operation. 

1. A unitized pump system comprising a housing having a fluid supply means and an outlet port; a drive means disposed in said housing; a first, second and third pump means disposed in said housing, each of said pump means having a discharge means extending to said outlet port for conveying the output of each pump means thereto, each of said discharge means of said pump means including a check valve, each of said pump means having separate inlet means for receiving fluid from said supply means, the inlet means of said third pump means including a valve means for selectively opening and closing the inlet means of the third pump means to control the output therefrom, the second pump means includes means to feed a small amount of the output fluid from said outlet port to said second pump means so that said second pump means is prevented from overheating when the valve means of the inlet means of the third pump means is in an open position; said second and third pump means being connected to said drive means; and a coupling means including a control means for selectively interconnecting said first pump means to said drive means.
 2. A unitized pump system according to claim 1, wherein said first pump means is a gear pump and said second and third pump means are centrifugal pumps.
 3. A unitized pump system according to claim 1, wherein said fuel supply means includes a fourth pump means connected to said drive means.
 4. A unitized pump system according to claim 1, wherein said drive means includes a drive shaft for each of said pump means, and gear means interconnecting each of said drive shafts so that each of said shafts and their respective pump means are driven by said drive means at a different speed.
 5. A unitized pump system according to claim 1, wherein said third pump means is a high-capacity pump means, and wherein said valve means includes a valve seat formed in the inlet means of said third pump means, a valve member coactable with said valve seat and attached to an actuator means disposed in said housing, said actuator being controlled by a sensor means responsive to flow demands of the fluid passing through said outlet port, so that when a high-capacity output is required from said system the actuator moves the valve member to an open position enabling the high-capacity slide means to begin pumping.
 6. A unitized pump system according to claim 1, wherein said means to feed of the second pump means is a small bleed orifice provided in the check valve of the discharge means for the second pump means.
 7. A unitized pump system according to claim 1, wherein said control means of said coupling means is interconnected to the discharge means of the second pump means so that said control means is actuated by a preselected output pressure of said second pump means to disengage said coupling means.
 8. A unitized pump system according to claim 7, wherein said coupling means is a fluid coupling having fluid input and discharge lines extending to a fluid pressure source, and said control means further includes a spool valve assembly disposed on said housing controlling flow in said input and discharge lines, the valve member of said spool valve assembly being moved to a position closing the inlet lines and opening the drain line by a preselected output pressure of said second pump means.
 9. A unitized pump system according to claim 1, wherein the discharge means of the first pump means includes a pressure control means to divert a portion of the output flow of the first pump means to said fluid supply means.
 10. A unitized pump system according to claim 9, wherein said pressure control means includes a pressure regulator valve means being adjusted to maintain a predetermined discharge pressure of said first pump means, a control bleed means connected to the outlet of said regulator valve means for increasing the discharge pressure of said first pump means, and a bypass valve means connected between the outlet of the regulator valve and the outlet of the control bleed means to selectively bypass the control bleed means.
 11. A unitized pump system according to claim 10, wherein said bypass means includes a temperature responsive unit disposed in the outlet of the control bleed means, said temperature responsive means being connected to a valve member of the bypass valve means so that said bypass valve member is moved to an open position when the temperature in the outlet of the control bleed means reaches a predetermined temperature to prevent overheating of the fluid passing through said outlet of said control bleed means.
 12. A unitized pump system comprising a housing having a fluid inlet means and an outlet port; a booster pump disposed in the inlet means, said booster pump having a discharge passageway in said housing; a cranking stage disposed in said housing, said cranking stage having an inlet in communication with the discharge passageway of said booster pump and having a discharge line communicating with said outlet port; a low-flow stage disposed in said housing and having an inlet means in communication with the discharge passageway of said booster pump and a discharge line communicating with said outlet port; a high-capacity stage disposed in said housing having an inlet means in communication with the discharge passageway of said booster pump, said inlet means of said high-capacity stage including a valve means for selectively opening and closing said inlet means to control flow of fluid to said high-capacity stage, said high-capacity stage having a discharge line communicating with said outlet port, each of said discharge lines having a check valve, vent means between said outlet port and the discharge line of the low-flow stage to deliver fuel for cooling said low-flow stage when fuel is delivered by said high-capacity stage, a drive means disposed in the housing for driving each of said stages and the booster pump, said drive means including a coupling means for selectively interconnecting the drive means with said cranking stage, said coupling means including a control means for selectively engaging and disengaging said coupling so that said cranking stage is selectively driven by said drive means.
 13. A unitized pump system according to claim 12, wherein said coupling means is a hydraulic coupling having a fluid supply port and a fluid drain port with the movement of fluid through said ports being controlled by said control means.
 14. A fuel pump assembly for aircraft engines comprising a fuel supply pump, a high-speed positive displacement cranking stage pump receiving fuel from said supply pump, a high-flow centrifuGal pump also receiving fuel from said fuel supply pump, a low-flow centrifugal pump also receiving fuel from said fuel supply pump, said high-speed positive displacement cranking stage, low-flow centrifugal pump and high-flow centrifugal pump each having a separate discharge passage communicating with a common outlet, a check valve between each separate discharge passage and said common outlet, a sensor controlling fuel flow to said high-flow centrifugal pump for controlling fuel discharge therefrom, vent means between said common outlet and the discharge passage of the low-flow centrifugal pump to deliver fuel for cooling said low-flow centrifugal pump when fuel is delivered by said high-flow centrifugal pump, means for driving said pumps, a disconnect coupling between said means for driving and said high-speed positive displacement pump, means controlled by pressure of fuel delivered from said low-flow centrifugal pump for disconnecting said coupling at a predetermined fuel pressure, whereby fuel from said fuel supply pump is pumped by said high speed positive displacement pump during engine cranking operations, is pumped by said high-flow centrifugal pump during high-powered engine operation and is pumped by said low-flow centrifugal pump during engine cruising operation. 